The test command
The test command is a unix command. It is not a shell builtin command. It can test the existence and status of a variable, or to make comparisons on variables, files, ...
Test returns 0 if the condition is verified. We call the command, via test or [].
Comparing integers
-eq
-
equals
if [ "$a" -eq "$b" ]
will be true if the numbers contained in $a and $b variables are identical.
-ne
-
is not equal to
if [ "$a" -ne "$b" ]will be true when the numbers contained in $a and $b variables are not identical.
-gt
-
is greater than
if ["$a" -gt "$b" ]will be true when the number contained in $a variable is upper than the number contained in $b variable.
-ge
-
is greater than or equal to
if [ "$a" -ge "$b" ]will be true when the number contained in $a variable is greater than or equal to $b.
-lt
-
is less than
if [ "$a" -lt "$b" ]will be true when the number contained in $a variable is less than to $b.
-le
-
is less than or equal to
if [ "$a" -le "$b" ]will be true when the number contained in $a variable is less than or equal to $b.
Comparing strings
=
-
equals
if [ "$a" = "$b" ]
will be true when $a and $b strings are identical.
!=
-
is not equal to
if [ "$a" != "$b" ]will be true when $a and $b strings are not identical.
<
-
that is smaller, according to the alphabetical ASCII order
if [[ "$a" < "$b" ]]
if [ "$a" \< "$b" ]Note that < needs to be in an escape sequence if it is inside of [].
>
-
is greater than, according to the alphabetical ASCII order
if [[ "$a" > "$b" ]]
if [ "$a" > "$b" ]Note that > needs to be in an escape sequence if it is inside of [].
-z
-
The string is empty. That is to say that it has a zero size
if [ -z "$a" ]
-n
-
The string is not empty.
if [ -n "$a" ]
Testing files
-e
-
Check if file exists
if [ -e "$fichier" ]
will be true if the file exists.
-r
-
Check if the file is readable
if [ -r "$fichier" ]will be true if the file exists and is readable.
-w
-
Checks if the file is writable
if [ -w "$fichier" ]will be true if the file exists and is writable.
-d
-
Checks if the directory exists
if [ -d "$repertoire" ]will be true if the directory exists.